Making lubricating oils by hydrotreating and dewaxing



United States Patent ice US. Cl. Edi h-33 6 @laims ABSTRACT Ell THEBESLSURE A process for producing a finished lubricating oil of enhancedquality, e.g. reduced pour point, from lubricating oil base stockscomprising substantially components boiling below 800 F. and containingmore than 0.75 percent by weight sulfur by subjecting such base stock tohydrofinishing and then dewaxing the hydrofinished base stock.

This application is a continuation-in-part of our copending applicationSer. No. 533,450, filed Mar. 11, 1966 and now abandoned.

Our invention relates to an improved process for producing lubricatingoils from certain high sulfur content stocks.

It has previously been suggested in the art to prepare lubricating oilsby subjecting crude lubricating oil stocks to a variety of treatmentsincluding deasphalting, solvent extraction, comparatively severehydrogen treatment sometimes called hydrotreating, solvent dewaxing,acid treatment, clay contacting and more recently, mild hyrogentreatment sometimes called hydrofinishing. This last mentioned mildhydrofinishing operation in many instances is employed in lieu of acidtreatment and clay contacting and is employed mainly in the treatment oflubricating oil base stocks, as distinguished from crude lubricatingoils, in order to remove odor and color forming materials which areconsidered to be objectionable in the final lubricating oil product. Allof the abovementioned operations contribute to the production of thefinal finished lubricating oil from the crude lubricating oil stock byremoving undesirable constituents and/or hydrocarbon types from eitherthe crude lubricating oil stock or the intermediate lubricating oil basestock. Generally, the prior art does not suggest any preferred order inwhich these various operations are to be conducted other than thatdictated by economic or engineering expediencies such as, for example,employing previously a treating technique which is effective to removematerials deleterious to subsequent treatment steps or which reduces thequantity of material to be treated in a subsequent step, the operationof which is more expensive.

One of the required characteristics or properties of a finishedlubricating oil is that it have a low pour point. The desired level ofthe pour point of a finished lubricating oil varies, dependent upon thetype of finished lubricating oil desired as a product and its intendedemployment. Usually, however, a pour point of +10 F. or lower isrequired. In some instances the desired pour point may even be as low asF. or even lower. In most instances, however, a finished lubricating oilhaving a pour point of about 5F. to about F. is satisfactory. The arthas recognized for many years that the pour point of a lubricating oilis generally related to the quantity of wax present in the material anda variety of dewaxing techniques have been suggested to lower the Waxcontent of lubricating oils and concomitantly 3,520,796 Patented July14:, 1970 lower the pour point thereof. Fresently, the techniqueemployed widely in the art is a solvent dewaxing operation. Even thoughpresent day solvent dewaxing techniqucs are generally considered to besomewhat of an improvement over techniques previously employed in theart, the solvent dewaxing treatments are still beset by the traditionalproblem in the dewaxing field, i.e. the wax cannot be removed from thelubricating oil without cooling the material being treated to anextremely low temperature usually lower than the desired pour point ofthe finished product. Thus, the limiting factor in most solvent dewaxingoperations is the refrigeration capacity of the unit and any techniquewhich would permit obtaining the desired pour point of the treatedmaterial but permitting employment of a dewaxing temperature even a fewdegrees above what might otherwise be required, results in a substantialimprovement and enhancement of the process from an economic view point.

In many instances this desirable characteristic of a low pour point in alubricating oil can be obtained when employing a solvent dewaxingtreatment in combination with any one or more of the treating techniquesmentioned previously. A typical example of the prior art operationincludes solvent dewaxing an intermediate lubricating oil base stockfollowed by acid and clay contacting of the dewaxed base stock. In moremodern refinery operations this scheme would require solvent dewaxing ofa lubricating oil base stock followed by hydrofinishing of the dewaxedmaterial to yield the finished lubricating oil. While this sequence ofoperations may in some instances be entirely satisfactory to yield alubricating oil having the desired pour point in an economical manner,it has been found that in many instances this sequence is notadvantageous.

We have discovered that when treating certain types of lubricating oilbase stocks the sequence of solvent dewaxing followed by hydrofinishingor of hydrofinishing a substantially wax-free lubricating oil base stockeither produces a finished lubricating oil having a pour point which ishigher than desired or requires a dewaxing operation employing anincreased refrigeration capacity in order to obtain a sufficiently lowdewaxing temperature and thus obtain a finished product having thedesired pour point. Further, we have discovered that when treatinglubricating oil base stocks of this particular type, it is necessary tohydrofinish the base stock and then to subject the hydrofinished stockto a solvent dewaxing treatment.

The particular materials to which the process of our invention isapplicable can be described as comparatively low boiling, high sulfurcontent lubricating oil base stocks. By the term lubricating oil basestock is meant a fraction or group of fractions usually produced at anintermediate point in the production of a lubricating oil which lacksbut the final finishing operations, such as, for example,hydrofinishing, acid treatment or clay contacting, before being classedas a finished lubricating oil. Generally, such lubricating oil basestocks can be obtained from crude lubricating oil stocks, i.e. untreatedmaterials boiling in the general range of lubricating oils, byatmospheric and vacuum distillation followed by deasphalting, such aspropane deasphalting, solvent extraction, treatment in a Duo-Solprocess, comparatively severe hydrogen treatment, i.e. hydrotreating,etc. or any combination of one or more of these treatments or none,depending upon the type of crude lubricating oil stock being consideredand the type of finished lubricating oil desired as product.

Generally, the lubricating oil base stocks treated in accordance withour invention are comprised substantially of components boiling belowabout 800 F. Lubricating oil base stocks having a 90 percent point ofabout 830 F. or lower are quite suitable. Lubricating oil base stockshaving a 90 percent point of less than about 800 F. can be treated inaccordance with the process of our invention with particularlyadvantageous results. These comparatively low boiling lubricating oilbase stocks will generally be found to have an average molecular weightof less than about 375 and will usually have an average molecular weightof about 350 or even lower.

The lubricating oil base stocks treated in accordance with our inventionmust also have a sulfur content of at least about 0.75 percent byweight. Usually these materials will be found to have a sulfur contentof at least 1.0 percent by weight.

The process of our invention is suitable for treatment as an entity ofthe entire spectrum of lubricating oil base stocks meeting the abovedescription as well as treatment of individual lubricating oil basestock fractions. These individual fractions generally have a range fromabout 90 to about 120 F. between their percent and 90 percent points andare usually considered as having a nominal spread of about 100 F.between their 10 percent and 90 percent points. The process of ourinvention can also treat the lubricating oil base stocks described aboveeither alone or in admixture with other lubricating oil base stocks.

It is believed that these lower boiling lubricating oil base stockswhich also have a comparatively high sulfur content initially, i.e.before hydrofinishing, comprise certain sulfur containing moleculeswhich upon hydrofinishing and the removal of sulfur therefrom eitherform waxy components themselves, are converted to certain compoundswhich although are generally not considered to be waxes have the samedeleterious effect on the pour point as do waxes, or are converted tonon-sulfur containing compounds which lack the solubilizing effect uponwaxes which the corresponding sulfur containing materials have. Thisphenomenon appears to be borne out by the fact that lubricating oil basestocks having a comparable boiling range but having a comparatively lowsulfur content do not exhibit this effect upon hydrofinishing.

Of the three major types of hydrogen treating operations generallyassociated with the lubricating oil field, i.e. hydrocracking,hydrotreating and hydrofinishing, the hydrogen treating operationemployed in our invention is termed hydrofinishing. Generally,hydrocracking is an extremely severe operation wherein comparativelyhigh boiling hydrocarbons, e.g. stocks containing components boilingabove the general lubricating oil range or above 1000 F., are treated soas to effect somewhat random severing of carbon-to-carbon bonds, therebyresulting in a substantial overall reduction in molecular weight andboiling point of the treated material while concomitantly effecting asubstantial increase in API gravity in order to produce large quantitiesof materials boiling below about 600 F. and a somewhat lesser quantityof materials boiling in the lubricating oil range from about 600 toabout l000 or 1100 F. In hydrocracking, at times, the production oflubricating oils can be merely incidental to the production of gasolineand furnace oil.

The next most severe hydrogen treating operation is termed hydrotreatingand is generally considered to be intermediate hydrocracking andhydrofinishing in its severity. Thus, hydrotreating effects asignificant amount of molecular rearrangement, while not effecting theexcessive and random breakdown of molecules effected in hydrocracking.Generally hydrotreating is primarily employed for the saturation ofaromatics but is still sufficiently severe so as to effect, at times, asignificant reduction in boiling range of the treated material.

Finally, the least severe hydrogen treating operation, termedhydrofinishing, operates primarily for the removal of minor quantitiesof contaminants and colorforming bodies found in lubricating oils orlubricating oil base stocks. Thus, hydrofinishing is effective, forexample, to reduce the sulfur content of the materials treated alongwith other contaminants and color-forming bodies but does not result inany significant increase in API gravity or any significant reduction inthe boiling range of the treated material. Usually any increase in APIgravity effected by hydrofinishing will be less than about 5 API.Furthermore, at times it would even appear that the boiling range of thetreated material has even been increased somewhat as indicated by aslight increase in the ASTM 10 percent and even 30 percent points.Moreover, inasmuch as hydrofinishing does not effect any noticeablesevering of carbon-to-carbon bonds which is essential to an extensivedegree, in hydrocracking and which, at times, can be obtained inhydrotreating, hydrofinishing does not result in any reduction in thepour point of the material treated. Additionally, bydrofinishing doesnot effect any significant amount, if any, of saturation, such as, forexample, saturation of aromatics.

In the hydrofinishing operation of our process the operating conditionsemployed can include a temperature from about 400 to about 850 F. andpreferably from about 600 to about 750 F., a pressure in the range fromabout 800 to about 3000 p.s.i.g. and preferably from about 1000 to about2000 p.s.i.g., a liquid hourly space velocity in the range from about0.1 to about 10.0 and preferably from about 1.0 to about 4.0 volumes oflubricating oil base stock per volume of catalyst per hour and ahydrogen circulation rate in the range from about 1000 to about 20,000s.c.f./b. and preferably from about 2000 to about 7000 s.c.f./b. Thecatalyst employed in the hydrofinishing operation in accordance with ourinvention can be any of the hydrogenating catalysts wellknown in the artsuch as, for example, Group VI and Group VIII metals, their oxides andsulfides, or mixtures thereof, either alone or supported on a suitablecarrier. These suitable carriers generally include materials which haveextremely low cracking activity, if any, and can be described as havinga cracking activity significantly below 35 on the Kellogg crackingactivity scale. Usually such materials will have a Kellogg crackingactivity of less than about 25 and preferably less than about 20.Examples of catalysts which we have found to be advantageous for use inour invention are combinations of nickel, cobalt and molybdenum on analumina support such as, for example, a catalyst of the type describedin US. Pat. 2,880,171, and a combination of nickel and tungsten onalumina. Catalysts such as these can also contain a small quantity ofsilica such as, for example, less than about 5 percent by weight or evenlower.

In the solvent dewaxing treatment of our invention we have found thatany of the well-known solvents employed in the art to effect dewaxingare quite satisfactory. Generally, we prefer to employ methylethylketoneand toluene in about a 50-50 mixture as the solvent. The particulartemperature employed in the solvent dewaxing treatment in accordancewith our invention is usually about 5 F. or more above that requiredwhen not employing our processing sequence or is about the same as thattemperature which would be required to provide a product having thedesired pour point, usually about +10 F. or lower, when treating a lowsulfur content material.

In order to illustrate our invention in greater detail, reference ismade to the following examples.

EXAMPLE I In this example several crude lubricating oil fractionsobtained from a reduced Kuwait crude having substantial componentsboiling above about 700 F. were separately subjected to solventextraction treatment after which the raffinates were combined andsubjecting to finishing operations including solvent dewaxing andhydrofinishing. One portion of the rafiinate was subjected to solventdewaxing-followed by hydrofinishing of the dewaxed raffinate, whileanother portion of the rafiinate was first subjected to hydrofinishingand then the hydrofinished rafiinate was subjected to a solvent dewaxingtreatment. The inspection data for the light neutral lubricating oilbase stock fraction of the raffinate is shown in Table I below.

TABLE I Pour point, F. 75 Sulfur, percent by wt 0.8 Distillation,vacuum, percent at F.:

The operating conditions employed in the solvent dewaxing treatment andin the hydrofinishing treatment in both the conventional solventdewaxing followed by hydrofinishing sequence and the hydrofinishingfollowed by solvent dewaxing treatment sequence of our invention weresubstantially the same with but one exception. Thus, the conditionsemployed in the hydrofinishing operation included a pressure of 1650p.s.i.g., a temperature, measured at bed outlet of about 700 F. and aliquid hourly space velocity of 3.0. In the solvent dewaxing treatmentthe solvent employed was a methylethylketone-toluene blend consisting of55 percent methylethylketone. The solvent to oil ratio for dilution wasfrom about 4.1 to about 4.3 and for the wash was 2.0. The one importantvariation in operating conditions between the two operations was in thetemperature employed in the solvent dewaxing treatments. In theconventional sequence a filtration temperature of F. was employed toprovide a dewaxed light neutral fraction having a pour point of 0 E,while in the solvent dewaxing operation in accordance with ourinvention, i.e. after hydrofinishing, the filtration temperatureemployed was only -10 F. The following Table II shows the inspectiondata for the finished light neutral lubricating oils obtained from thetwo processing sequences described above.

TABLE II Finished lubricating oil Dewaxing Hydrofinishing beforehydrofollowed by 6 From a comparison of the inspection data in Table IIabove it will be noted that in all other physical properties exceptingpour point the two finished light neutral lubricating oils aresubstantially identical. Significantly, however, the lubricating oilproduced in accordance with the process of our invention has a pourpoint 5 F. lower than that of the material produced in accordance withthe more conventional operation. It will also be noted that this lowerpour point was obtained when dewaxing at a temperature 5 F. higher thanthat employed with the more conventional operation. Thus, quiteunexpectedly, it will be seen that finished products having a lower pourpoint are obtained when employing a higher filtration temperature in thesolvent dewaxing treatment in accordance with our invention. To expressit in another manner, this data would indicate that when treating a lowboiling, high sitfur content lubricating oil base stock and dewaxingsuch base stock prior to hydrofinishing, a filtration temperature mustbe employed which is at least about 25 F. lower than the desired pourpoint of the finished product whereas in operating in accordance withthe process of our invention a filtration temperature of only 15 F.lower than the desired pour point of the finished product can beemployed. This constitutes a 10 F. savings in refrigeration capacity.

EXAMPLE II In this example a blend of light neutral distillates obtainedfrom an Ordovician crude and a Delta lube mixture, which blend had theinspection data shown in Table III below, was subjected to a furfuralextraction and the rafiinate from the extraction was then subjected to asolvent dewaxing treatment. In the solvent dewaxing treatment thesolvent employed was a methylethylketone-tolu ene blend consisting ofpercent methylethylketone. The solvent to oil ratios for the initial andsecondary dilutions were 0.6 and 1.4, respectively, while the solvent tooil ratio for the wash was 1.0. A filtration temperature of 6 F. wasemployed. This solvent dewaxing treatment provided a hydrofinishingcharge stock having the inspections also shown in Table III. Afterhydrofinishing, the dewaxed and hydrofinished product was analyzed andthe inspection data obtained is shown in Table III. For purposes ofcomparison, the inspection data for the raffinate of Eaxmple I as wellas the inspection data for the finished lubricating oil obtained bydewaxing and hydrofinishing such rafiinate in Example I are also shownin Table III.

TABLE III Dewaxed Dewaxed and hyand hydrofinishdrofinish- Rafifinate edrafilnate Dewaxed ed rafififrom Exfrom Ex- Charge Rafiflnate rafilnatenate ample I ample I Gravity, AII 29. 3 33. 8 33.1 33.0 32. 3

i SUS at- FSO F 103. 3

150 F 55. 0 53. 4 210 F 30. 8 39.6 30. 7 Viscosity index 87 114 102 Pourpoint, F. 0 Color, D 1500 L 3.0 L 1. 5 L 1.0 Sulfur, percent by weight0.20 0. 08 O. 08 Distillation, vacuum, F.:

7 From the inspection data shown in Table III above for the solventextracted ratfinate, it will be seen that the intermediate lubricatingoil base stock obtained from the blended crude lubricating oil stock,although having a 90 percent boiling point of 795 F., has a sulfurcontent substantially below 0.75 percent; to wit 0.20 percent. From anexamination of the data shown for the hydrofinished product obtainedfrom this raffinate after dewaxing, it will be seen that a satisfactorypour point of F. was obtained and that a dewaxing temperature of onlyabout 6 F. was required to produce this pour point in the finishedlubricating oil. A comparison of the results obtained in this examplewith the resultant product obtained from the high sulfur contentmaterial of Example I when employing the same operating sequence, asshown in the last two columns of Table III, demonstrates that whentreating a feed stock having a very similar boiling range but having ahigh sulfur content, i.e. above about 0.75 percent, even more severedewaxing conditions, e.g. a filtration temperature of F., is not capableof producing a finished lubricating oil having an equally low pourpoint.

EXAMPLE III In this example a lubricating oil base stock comparable tothat described as the raffinate in Example II is subjected tohydrofinishing under mild hydrogenating conditions in the presence of ahydrogenating catalyst. Subsequently, the hydrofinished base stock issubjected to a solvent dewaxing treatment employing amethylethylketone-toluene blend as the solvent and a filtrationtemperature in the range from about -l0 F. to about 5 F. Inspection ofthe finished lubricating oil obtained by hydrofinishing and thendewaxing this comparatively low boiling, low sulfur content lubricatingoil base stock shows that the pour point of the product is notsubstantially different from that obtained when employing the operatingsequence of Example II. It will be seen, therefore, that the process ofour invention, requiring dewaxing subsequent to hydrofinishing, isoperable when treating a comparatively low boiling, high sulfur contentstock but that when treating a comparatively low boiling, low sulfurcontent stock there does not appear to be any advantage to be gainedregarding the pour point of the finished product through employment ofour inventive process.

We claim:

1. An improved process for the production of a finished lubricating oilfrom a lubricating oil base stock 8 comprised substantially ofcomponents boiling below about 800 F. and containing at least about 0.75percent by weight sulfur which comprises subjecting the lubricating oilbase stock to hydrofinishing by contacting it with hydrogen in thepresence of a hydrogenation catalyst comprising a hydrogenatingcomponent selected from the group consisting of (a) nickel, cobalt andmolybdenum and (b) nickel and tungsten supported on a carrier having acracking activity on the Kellogg scale of less than about 25 underhydrofinishing conditions of pressure, space velocity and a temperaturefrom about 600 to about 750 F. thereby effecting removal ofcolor-forming bodies from the lubricating oil base stock without anysignificant reduction in boiling point, saturation of aromatics orreduction of pour point and then subjecting the hydrofinished base stockto a solvent dewaxing treatment.

2. The process of claim 1 wherein the lubricating oil base stock has apercent boiling point of less than about 830 F.

3. The process of claim 1 wherein the lubricating oil base stock has a90 percent boiling point of less than about 800 F.

4. The process of claim 2 wherein the lubricating oil base stock is afraction having a range from about 90 F. to about 120 F. between its 10percent boiling point and its 90 percent boiling point.

5. The process of claim 3 wherein the lubricating oil base stock is afraction having a range from about 90 F. to about 120 F. between its 10percent boiling point and its 90 percent boiling point.

6. The process of claim 1 wherein the lubricating oil base stockcontains more than about 1.0 percent by weight sulfur.

References Cited UNITED STATES PATENTS 2,787,582 4/1957 Watkins et al.208-58 3,142,634 7/1964 Ireland et al 208- 3,012,963 12/ 1961 Archibald208-264 3,285,848 11/1966 Donaldson et al. 208-212 3,293,173 12/1966McCall 208212 3,318,800 5/1967 Ringler 208-18 HERBERT LEVINE, PrimaryExaminer US. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 i520. 796 Dated Julv 14 L 1970 n H. C. Murphy Jr. J. R. Murphy and H. C.Stauffer It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 66, "+50 F. should be +5F.--

Column 4 line 73 "subjecting" should be subjected-.

SIGNED AND SEALED 0C? 6 Attest:

Edward m. much i van-nun 1:. sum. .13- L Attesung Officer oomissioner ofPatents

